


All's Fair in Love and (Prank) Wars

by torrikor



Category: Undertale (Video Game)
Genre: F/M, M/M, Other, Prank Wars, Slice of Life, Slow Burn, Slow To Update, and bad jokes, and they were ROOMMATES (oh my gods they were roommates), frienemies to lovers, gender neutral reader, idiots to lovers, let swapfell siblings be Soft dang it, mostly??, my interpretation of swapfell/fellswap!! :D, petty bastards doing what petty bastards do best, the One True Trope, with some fluff and angst sprinkled in between
Language: English
Status: In-Progress
Published: 2019-05-09
Updated: 2019-05-19
Packaged: 2020-02-28 15:56:27
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 8,131
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18759631
Author URL: https://archiveofourown.org/users/torrikor/pseuds/torrikor
Summary: You grimace as you approach the kitchen, expecting abject chaos and being greeted by something just slightly more tame than that; Sans, the flatmate you’ve found to be the most stubborn person you’ve ever met, holding various kitchenware in his arms and keeping very very still on one leg as a china teacup balances on the crook between his nose ridge and the rest of his skull. A plate from the same set is supported by his foot, bent at a carefully awkward angle to stop it from falling. The very set a friend had gifted you years ago, in fact. Huh. You forgot you had those.“Do you… Need some help?”“No.”





	1. The Googly Eyes Prank

**_‘The fight for rights continues! New laws passed, but Monsters are still unsatisfied!_ **

_Four years ago, Monsters were released from the now infamous Mt. Ebott – and what a sight to behold! Thousands have since emerged from the mountain, and new laws have since emerged from governments all over the globe. The Monsters’ ambassador, the same human child responsible for freeing them, has been working closely with higher-ups and the Monsters' former Empress to secure basic rights to accommodate the world’s most recent phenomenon; and yet despite all the changes there is still much work to be done!_

_Hate crimes towards Monsters in the US have lowered in the past year, according to the recently disclosed report from police across various cities. One of the newest additions to a Monster’s rights aims to help further prevent- ‘_

 

“Human! The spices, where did you say they are kept?”

You glance up from your laptop towards the door, where your newest acquaintance is leaning into the room. He balances his weight on the door handle and frame, and you catch him briefly scanning the room before his attention settles on you. Adjusting your sitting position, you gesture vaguely towards the kitchen. “Cabinet on the left, probably right at the back.”

“If we are to be living together, I hope you realise that I will be reorganising where things are kept in the kitchen as soon as possible,” Your flatmate tuts, standing up straight and crossing his arms, “It is an absolute _mess_ in there, I’m half convinced you don’t know what a cooking space is supposed to look like.” With that charming remark, he turns on his heels and leaves.

You glare at the space where he once was, then lightly shove your laptop away and get up to close the door. Even if you’re not used to living with other people, having been on your own these past few years, you’re pretty sure that closing the door behind oneself is considered common decency. And, considering that your new flatmate has been on the surface and integrated in human culture for four years now, he has absolutely no excuse not to abide by the laws of curtesy.

At first, you’d figured he wouldn’t be that bad. You didn’t want to judge, after all; unlike a great number of humans you’ve met, you have no problem with Monsters being around. So why not give him a chance? He was the only one to respond to your request for a flatmate to half the rent with, so your choices were limited as it was. Now, though, perhaps you’d been mistaken in your initial judgement. He’s commanding, he’s arrogant, and judging by the unholy crash that just came from the kitchen, he’s not the best cook (despite outright _insisting_ on making dinner).

The noise stopped you before you could return to your browsing, and you only waited long enough to click off the article you’d been reading before jogging out into the hall.

More noise. Pots and pans and plates, cutlery and china knocking together and causing an awful assault on your ears. You grimace as you approach the kitchen, expecting abject chaos and being greeted by something just slightly more tame than that; Sans, the flatmate you’ve found to be the most stubborn person you’ve ever met, holding various kitchenware in his arms and keeping very very still on one leg as a china teacup balances on the crook between his nose ridge and the rest of his skull. A plate from the same set is supported by his foot, bent at a carefully awkward angle to stop it from falling. The very set a friend had gifted you years ago, in fact. Huh. You forgot you had those.

“Do you… Need some help?”

“No.”

There are more plates on the floor at his feet, one or two of which are shattered and others bearing newly obtained chips and cracks. You make sure to keep clear of them. Perhaps you’d be mad that he broke your very-expensive-and-also-a-gift set of kitchenware, if you weren’t currently staring at the rest of the kitchen. While Sans carefully starts setting things down on the counter – keeping his eyelights laser-focused on the teacup throughout -, you stare at the glittery splatters of what you can only assume is food scattered about on the stove, the sink, and part of the wall.

Edging around the shards of plates, you lean over to turn down the heat of the oven, afraid something might catch on fire. On the small, cheap table by the window sits a plate of… something, smoking and smelling absolutely rancid. You can’t help but cringe when you get a whiff of it. Is _that_ what he had been cooking?

“I _said_ I don’t need your help, human,” Sans finishes disarming himself of the most delicate set of kitchen-themed armour, setting the last plate down and side-glaring at you. The jagged scar down his eye distorted the eyesocket slightly. “I am perfectly capable of taking care of this myself, _thank you.”_

You glance once more around the mess that is currently your kitchen. “You sure ‘bout that?” Your eyes settle on him, then flick down to the floor and back again, “You broke the good plates, those were a present, man- “

“I will replace them.”

“I’d rather you just apologise, honestly.”

“What for?” You don’t like the accusatory tone he uses as he turns sharply to face you, “It is _your_ fault that they fell in the first place! Had they not been so haphazardly stacked, this wouldn’t have happened-!”

“You’re seriously blaming me for this?” You push past him and crouch down to rummage through a cupboard, searching for a dustpan and brush. _This_ was what got on your nerves – not that he’s a Monster, but the fact that he was far too egotistical to be tolerable. If you’re going to be living with him, he’s going to have to take it down a couple notches.

Finding what you need, you pivot on your heels and get to work cleaning up the floor. Above you, Sans grumbled something as he starts to – you assume – reorganise the kitchenware in the cupboards. He never replies to your question.

“I also have a name, y’know.”

“I am aware.”

There’s no end to it, is there? You want to rebuke him, but his tone was incredibly final. And, as open-minded as you consider yourself to be, there’s no denying the nagging fear that creeps up whenever you think of angering him. Monsters are capable of much, much more than humans; and you’re in no rush to find out what Sans is like when he’s truly angry.

You heave a frustrated sigh and sit back on your knees to look up at him as he busies himself with stacking dishes. Monsters, you’ve found, are ridiculously tall by human standards – that height difference is emphasised now that you’re kneeling. Many Monsters are also equipped with claws and fangs, and Sans is no different; the sharp tips of his phalanges scrape lightly against each piece of china he picks up. They’re the only exposed parts of his hands, the rest of the bone being covered by fingerless leather gloves. Now that you think about it, you’ve yet to see him take those gloves off.

“It’s rude to stare.” The navy slits of magic that serve as his pupils flick down towards you, appearing much like a cat’s eyes – you avert your gaze and instead focus on the plate of indiscernible burnt food. A weak grimace starts to form on your face just at the sight of it on the other side of the room, you can’t even bear to think about what it might taste like.

“What… Were you trying to make..?” You venture, standing to then dump your collected plate shards into the bin.

_“Croquetas,”_ Sans responds, temporarily adopting an accent you didn’t realise he was capable of, “À la Human – although I must admit I did not expect them to explode. Human food responds terribly to magic.”

“Is that why there’s food stains everywhere?” 

“No shit.”

You almost laugh – Sans is nothing if not eloquent, that much you can tell from the few days he’s been your flatmate, and if memory serves this is the first time you’ve heard him swear. You then remember that you’re mad at him.

“Okay, then what’s dinner gonna be? I don’t know how it works on your side of things, but I guarantee you that _that,”_ You point towards the plate, “Is not human-stomach friendly. Why’d you even insist on making dinner if you don’t know how to cook?”

Perhaps you could have worded that a bit better, as he is very quick to glare at you again. “I am an _excellent_ cook, for your information – the issue here is that you don’t have any monster food, which is infinitely more substantial, responds well to magic, and is something that I can actually eat.”

Truthfully, you haven’t had the time nor money to go grocery shopping yet, but you fail to bring this up as another fact takes your interest. “You… Eat?” You realise a second after speaking that you probably sound rather ignorant, however Sans is faster to quip back at you.

“Of course I eat! What kind of a question is that?”

“In my defence, you’re a skeleton.”

“I am, first and foremost, a _Monster._ A living being. I require sustenance just like anyone else,” It hadn’t registered before, but you can hear the slow _tap tap tap_ of his heel against the tiled floor, “I don’t expect you to know everything to do with us, but _at least_ know that Monsters can only eat magic-infused food.”

“Magic food only, got it,” You hold up your hands in an attempt to placate him, but the gesture only seems to make him tense, “I’ll see if I can go shopping tomorrow, getting some groceries has been long overdue, anyways- “

“You are _not_ shopping for me, either I go with you or by myself.”

“Fine! Fine, do whatever. Just.. Get out of the kitchen while I clean this up,” You crouch again to stack the salvageable plates and bin the ruined ones, only to have them yanked out of your hands as soon as you stand. Your reply is an indignant _“Hey-!”_

Sans sets the stack of plates down away from you before proceeding to direct you out of the kitchen by your shoulders. This is not difficult, as along with being much taller, he is also much stronger than you. “Absolutely not. If you cannot arrange china sets correctly I fear what you’d do trying to clean volatile magic food.” Of all the thing’s you’ve heard, ‘volatile magic food’ is definitely a new one.

“You can’t just kick me out of my own damn kitchen- “

“Our damn kitchen.”

“-Especially when _you’re_ the one who made the mess in the first place!”

“Then what am I doing right now?” Despite the fight you put up, he has still successfully escorted you back into the living room, where he finally releases your shoulders. You turn and are tempted to try and bypass him back into the kitchen – however the standing in your way and crossing of his arms tells you he has other ideas.

You mimic his stance, jutting your chin out as you look up at him. _“Right now,_ you’re being an ass.” His only response is a scoff. Sans then returns to the kitchen and leaves you where you are, squinting after him as if glaring at his back will convey your annoyance. Eventually, you relent and idly scuff your foot over the carpet, grumbling under your breath, “Fine, I’ll just order a pizza or something.”

###### 

By the next morning, you decide on the perfect way to retaliate; harmlessly hilarious, yet persistent pranks. You have the day off work, as well, which is perfect – what you have in mind will take a while. Once you’ve undergone your morning routine, you enter the kitchen with a skip in your step, the thought of putting your plan into action already inciting a childish giddiness in your demeanour. Sans isn’t there, but the kitchen is spotless, like something you’d see in a magazine. Which, dare you admit it, is quite a feat considering how low-class your apartment is. You pull the small jar on the nearby counter towards you, something you’ve made a habit of dropping any savings in, and fish out the money you’ll need. Might as well stock up on food while you’re out, as well.

After locking the door behind you and taking the elevator down to the first floor, you give an idle mock-salute to a passing neighbour as you make your way out of the apartment complex. The building is nice enough, if a little run down, and the people living next door to you are polite whenever you see them. Things could definitely be worse.

The air is frigid when you exit, sapping the heat from your body in record time. You pull your jacket closer around yourself and are on your way down the street. Your usual place for groceries is only a few minutes’ walk away, but to get your prank supplies you may need to go further into town to find a crafts store, or something to that effect. With any luck, you can find somewhere that sells what you need for cheap.

As you walk, you let autopilot take over as you recede into your thoughts, reviewing events and current happenings and debating what you should have for lunch. Your mind inevitably drifts to the subject of your flatmate, and you find yourself going over what you know about him.

What you know about him is… Not a lot, actually. You know he has a younger brother, rooming with someone down the road due to there not being enough space for both of them. You know they didn’t manage to sell their Gold before the market crashed, leaving them in a similar monetary situation to yourself. Beyond that, Sans is practically a mystery. An egotistical, stubborn mystery. What’s his deal, anyway? You realise that the Underground was a harsh place to live – you’ve heard stories about what happened down there that would fall well under the horror genre – but… That was four years ago. You don’t expect anyone to have changed completely in that time, but some change must have occurred, right? There’s no reason you can see for Sans to still be so… So the way he is. You’re not sure how to describe it other than ‘difficult’. Was that being too insensitive?

Arriving at your destination draws you from your gradually derailing thoughts, and you hurry inside to get out of the cold morning air. Still partially on autopilot, you do your usual rounds – now with added consideration as to what kinds of food Sans might want. You don’t plan on getting anything for him, he said not to after all, but the wondering about his tastes is still there as you pass each aisle. Once you’ve payed everything you need (and can afford), you begin the slightly longer trek towards the busier side of town.

You adjust to the temperature outside quicker this time, and border on power-walking in your determination to find what you need and get home to start working as quickly as possible. Weaving around people proves to be something you’re quite practiced at, particularly once you reach the town centre. It’s busy today, which you deem nothing out of the ordinary. You pause at a corner, both to catch your breath a little (Wow. You need to work out more) and to get your bearings. Even if you’re aware that the town centre exists, you’re not familiar enough with it to know where specific stores might be.

You hum to yourself as you glance around, scanning different signs and advertisements in search of something related to what you’re looking for. “If I was a crafts store, where would I be…” You mumble under your breath, beginning to walk again down a street you hope will start to look more familiar real soon. Maybe you should make yourself come into town more often, you’ve lived here long enough that you should know your way around by now. You turn another corner, and light up at the sight of a little store nestled in between a take-away place and some houses. With an _“Aha!”_ that’s much more triumphant than it probably should be, you cross the street and push the door open, a bell’s chime announcing your entrance.

The floorboards creak slightly with each step you take, and you have to dodge your way through various cluttered shelves and racks that fill up the already small interior. From what you can see, just a few people are browsing the items for sale, and a lone employee sits at the register near the back of the room. Various decorations adorn the windows, stained glass colouring the light shining through and creating a kaleidoscope of colours on the wooden floors and shelves. You pause for a moment to watch, and hum quietly to yourself. You never knew this shop was here.

 

Finding what you need proves somewhat difficult, and you find yourself getting impatient the longer it takes you. Is this what Sans felt like when he was trying to sort through how you organised the kitchen? Whenever you think you’ve figured out how the system works, there’s something that throws you for a loop – who puts glitter glue alongside ball-joint dolls? You eventually resign yourself to asking for help. Only… You’re not entirely sure who to ask.

While you hesitate, your confused and slightly annoyed expression mustn’t have gone unnoticed, as someone taps you on the shoulder to get your attention. You glance over your shoulder before turning completely, gaze following the hand as it withdrew to clutch a small whiteboard. The person’s arm is completely skeletal like your flatmate’s, yet much thicker than human bones and covered partially by a copious amount of bracelets. You have to crane your neck up to meet the Monster’s eyes, as well as take a step or two back. He has an unbuttoned plaid shirt over his uniform, with a nametag reading ‘Papyrus’ pinned to it.

He holds up the whiteboard for you to see, and you read it in favour of trying for a greeting. It seems as though a previous message was hastily rubbed out in order to make space for the new one;

_‘can i help you?’_

“Oh! Yeah, actually, I’m- Uh...” Even if he’s (you assume) an employee, saying what you’re looking for out loud strikes up a slight twinge of embarrassment. You manage to awkwardly grin through it, “I’m looking for, like.. Ya’know those googly eye things? I need as many of those as I can get.”

Papyrus is silent, but you notice the sharp line of teeth that comprise his mouth twitch upwards as if he’s trying not to smile. Light from the windows reflects off the gold canines on each side, drawing your eyes down towards them for a moment. As you do so, you pick up on how his shoulders are shaking slightly – he’s definitely trying not to laugh. Even as he gestures for you to follow him, you find yourself with a newfound heat on your face and a need to explain yourself.

“It’s! Um, it’s for my flatmate! A prank, I mean – a prank for my flatmate,” You mentally award yourself the title of ‘Shittiest Conversationalist’. Papyrus audibly snickers, though, which you’re not sure is good or not. He guides you to a corner of the shop and points to one of the higher shelves, and you practically light up in childish glee at the sight of a massive bag of googly eyes. _Perfect._

You go to reach for them, only to find Papyrus has beaten you to it as he holds the bag out for you. You practically beam at him, “Thanks! These’ll work great,” Adjusting your grocery bag to hang at your elbow, you take the plastic googly bag from him and start towards the register- before he stops you with a light hand on your shoulder again.

He lifts up his whiteboard and takes a marker out of a pocket, and you wait patiently as he writes something down. The movements are fast and precise, like he has a lot of experience making sure his writing is done quickly but still remains legible – considering you haven’t heard him speak this entire time, you’d wager that is definitely the case. When he lifts the board up for you to read, you can’t help but raise your eyebrows in surprise.

_‘you’re sans’ flatmate, right?’_

“How d’you-?” You begin to voice your question, then remember one of the two things you know about Sans and promptly grin in realisation, “Oh! You’re his brother?” Saving you the potential mortification of being wrong with that assumption, Papyrus nods and holds a hand out for you to shake, which you take with much less hesitation than you thought you’d have. His grip is laxer than you were expecting.

You briefly introduce yourself before once again hesitating, that same awkward grin from before appearing on your face. “You, uh… Don’t mind that I’m pranking your brother, right?” The question is accompanied by a sheepish half-laugh, half-cough – luckily for you, Papyrus immediately adopts a grin as mischievous as yours is hesitant. Even if you think you know his answer, he scribbles another sentence on the board for you:

_’i’d be disappointed if you didn’t.’_ You decide that you’re going to get along very well with Sans’ brother.

###### 

You exchanged numbers with Papyrus before leaving the store – he told (wrote?) you that it would be much easier for him to text than write with a pen if ever you should meet up with him again. Now, though, your phone is cast aside on the coffee table as you wait for Sans to return from wherever he’s been all day. Even if you feign being busy with your laptop, you’re actually just clicking absently between tabs, periodically glancing up at the door for any sign of his return.

Eventually, the handle turns, and you have to resist the urge to grin.

In your personal opinion, you do an excellent job of acting nonchalant and slightly annoyed upon Sans’ entrance (the annoyed part isn’t so hard – you’re still miffed at him), and casually lean back against the couch cushions as he pauses near the door to take his jacket off. You notice that he has a grocery bag similar to your own set by his feet.

“I met your brother in town today,” You start, which catches his attention about as quickly as you expected. Allowing yourself to feel just a little smug, you tilt your head slightly and smirk, “He’s a lot nicer than you.”

“Of course he is.” The sincerity catches you off guard, but you only raise an eyebrow as Sans picks up his bag and heads for the kitchen. That’s when you grin, subtly adjusting your position to look over your shoulder as inconspicuously as possible. Sans returns from the kitchen in record time, stopping a few feet away from you and crossing his arms like a disappointed parent. You try for your best innocent face.

“What the fuck did you do to my damn kitchen.”

“Our damn kitchen.”

Sans actually _growls,_ something you shrink back from much quicker than you’d like to admit. He takes one breath, and another, then lets his arms fall to his sides as he stares you down. In the back of your mind, you get the feeling of being judged for your actions, as if he’s trying to discern your true intentions. The sensation is uncomfortable, and you make a point to turn away and go back to clicking at your laptop. 

“If you wish to be immature about this, then so be it. You are not the only one capable of being childish.” That scrutinising feeling persists for a few seconds longer before disappearing, and you untense your shoulders. Is that Sans’ way of warning you of retaliation via more pranks? If it is, he really needs to lighten up, geez.


	2. The Food Prank(s)

**Summary for the Chapter:**

> _**You:** Cool, cool – hey just out of interest, his idea of revenge wouldn’t involve putting something in my food, would it?_
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> _**pyrus:** idk, why??_
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> _**You:** I have literally never had this much energy in my life_

For once, the smell of breakfast greets you when you wake up. When’s the last time you’ve been greeted with breakfast first thing in the morning? It’s been so long, you didn’t realise how much you missed it.

You have work today, and go about your morning routine as usual – that comes to a grinding halt as soon as you enter the kitchen, though. All your hard work from yesterday has been undone, but your attention is more preoccupied with the absolutely mouth-wateringly-good smell of whatever Sans is cooking. He seems just about finished, which is great timing.

“Wait, you can? Actually cook?”

“Yes. Did you think I was joking?” Honestly, you just thought he was being defensive and trying to one-up you. The way he glances at you over his shoulder, though, and raises an eyebrow (bonebrow?) with a smug smirk- he’s definitely still trying to one-up you. And succeeding, apparently. That fact annoys you.

You sit yourself down at the small table, tucked away under the window and still retaining the vague burnt smell from the previous cooking disaster. “I mean, kinda?” With a shrug on your part, and a head tilt on his, you lean down to tie your shoelaces as you continue, unable to resist a small jab at his expense, “You honestly cannot expect me to believe you could genuinely make something edible after those what’cha-ma-callits. Is whatever you’re making now even edible?”

 _“Croquetas,”_ Sans corrects, setting a plate down in front of you. You would almost call the gesture sweet, if it weren’t for the cocky grin on his face, “And I think you’ll find yourself eating those words.“

“Was that a-“

“You’d better hurry, don’t you have work today?” Your flatmate turns on his heel, returning to the counter and picking up a plate from the sink to begin cleaning it. You watch for a moment, refusing to acknowledge the pout working its way onto your face, before eventually resigning yourself to actually trying the food he made for you. Is that just… A thing that Monsters do? This is the second time he’s insisted on making food for you. Maybe he just thinks you’re incapable of doing it yourself – you end up latching onto that explanation and sneer down at the table. You wouldn’t put it past him to think that you’re _that_ helpless.

Stabbing a fork into the omelette in front of you is satisfying, though even if it smells heavenly you honestly don’t expect much. Apparently this was the wrong thing so expect, as you quickly decide this is the best breakfast you’ve ever had – Sans doesn’t need to know that, though. His ego needs to go down a notch and damn it you’re sticking to that verdict.

Unfortunately for you, the mild surprise works itself onto your face, and that annoyingly cocky grin Sans is sporting becomes an annoyingly _smug_ grin in record time. He finishes with the plates in the sink, setting them out to dry and idly straightening the cuffs of his shirt as he passes you, practically the embodiment of self-confidence. The front door is his next destination, pulling a jacket over himself in one seamless motion before he calls to you over his shoulder in a sing-song voice, “You’re welcome, human-!”

Oh, that _bastard._

It was not a humble ‘you’re welcome’ at all, and you get the feeling that was intentional. Looks like _someone_ didn’t learn from your previous ‘scheme’ – you’ll have to think of another, one he can’t dismantle so easily. Later, though. You want to finish this breakfast first, then you need to head off to work. Before you can, there’s a light buzz accompanied by a chime in your pocket, and you pull your phone out to investigate.

_**pyrus:** mornin =<]_  
_**pyrus:** thats a skeleton face. its me smilin at u_

You find yourself smiling down at the screen; how could the world’s most stubborn asshole be related to the world’s gentlest giant? If only you knew the answer. Before you can even consider typing a reply, more messages come through – he’s a quick texter, it seems.

_**pyrus:** howd the prank go?? please tell me u got pictures of his reaction_  
_**pyrus:** did he swear revenge yet or can i postpone plannin ur funeral_

You snort at that, leaning back in your chair as you set about replying with one hand while the other occupies itself with shovelling more food into your mouth. Sans had made quick work of cleaning up yesterday’s prank – granted, you didn’t use particularly high-quality glue – but you’re fairly certain he’s too stuck-up to resort to petty ‘revenge’ like that.

_**You:** No pictures, unfortunately_

_**pyrus:** =<[_

_**You:** But I’m pretty sure there’s no need for a funeral – he just left the apartment, I’m guessing for work?_

Idly, you glance up at the clock to check for yourself how much longer you can stall before needing to get a move on. The diner isn’t far from your apartment, you should still have time to get yourself over there at this rate. As you’re considering this, you notice a faint tingling sensation on your tongue. Your first thought is to panic _– did that asshole put something in your food? -_ before it registers that, actually, it doesn’t seem to be anything particularly concerning. Odd, perhaps, but not harmful so far.

You’ve never experienced anything quite like this, though – the fuzziness, although concentrated on your tongue, spreads gradually throughout your body, and you find yourself practically buzzing with energy. What the _fuck_ kind of drugs did Sans put in your breakfast? The phone chimes again, and you only vaguely register your foot tapping against the ground as you read the new message.

_**pyrus:** yea hes on the mornin shift today_

_**You:** Cool, cool – hey just out of interest, his idea of revenge wouldn’t involve putting something in my food, would it?_

_**pyrus:** idk, why??_

_**You:** I have literally never had this much energy in my life_

In fact, you’re hardly sitting still in your seat at this point, having more energy than you know what to do with and more than ready to get up and do something. It feels as though you could run the long way to work and still make it there before your shift starts- speaking of, now’s as good a time as any to get yourself out the door and on your way to the diner. How long is this weird whatever-the-hell-was-in-your-food induced energy going to last, anyway? You don’t know, and you don’t have time to find out.

You wolf down the last of the omelette and pocket your phone despite there being another message waiting for you, making a mental note to check it later. The plate gets dumped in the sink to be washed at some point, and after slinging your bag over your shoulder you practically throw yourself out the door, having half the mind to lock it before taking off down the hallway. You’re pretty sure you aren’t even late at this point, but the almost otherworldly energy coursing through you has you feeling as if you could do anything. You even forgo the usual elevator and take the stairs. _The stairs!_

The street running alongside your apartment complex isn’t particularly busy this time of morning, which is rather fortunate as you find yourself booking it down your usual route to work. Does it make you feel like a late-for-school-trope anime character? Yes. Do you care? No.

You make it to work a whole fifteen minutes early, skidding around the back of the establishment to fling yourself through the staff only entrance and into the break room. There, a few co-workers are already scattered about, and you practically throw your bag into the space you’ve long since claimed before taking your apron off the hanger. It’s as you’re tying the strips of fabric behind your back that your youngest co-worker approaches. Although, calling her a ‘co-worker’ is only a formality – being the boss’ daughter, Fuku gets away with much more slacking than she probably should.

“That was quite an entrance,“ Her voice is low and crackles with each word, not unlike the fire her body is comprised of, “What brings you here so early?”

“I ran,” Is your vague reply. Honestly, it’s amazing that you’re not doubled over trying to catch your breath at this point. On the contrary; you’re bouncing on the balls of your feet as you secure the apron in place. Fuku giggles at your antics – a chittering sound that is in no way hindered by the hand she places delicately over where her mouth would be – before gesturing to the door.

“Alright, keep your secrets – you’re on Zip duty, by the way.” Ah. Yes. You forgot that it’s your turn to feed Zip today. The ridiculous amount of energy you’re currently supressing will come in very handy for that.

You nod as a means of acknowledgement, and pick up a notebook to slip into your pocket before you leave the staff room. Dealing with Zip is always a time-consuming endeavour, so you decide to get that over with first. It’s not like the task is a _bad_ one, per se, you actually quite enjoy hanging out with the rather monstrously sized salamander your boss keeps as a pet. They’re just very excitable and tend to forget the difference between ‘edible’ and ‘non-edible’, is all.

Zip is usually found tottering about between the booths out on the main floor, acting as quite the customer-magnet for humans in particular – something about a giant, magical, friendly reptile just can’t be ignored, you guess. You step out from behind the counter to look for them, offering a curt nod to your boss as you pass. Grillby isn’t much for words, you’ve found, but is a true master of conveying his messages through actions alone. Right now, you’re thinking that raised eyebrow is the standard ‘watch yourself’ look he gives to anyone on feeding duty. Not out of concern for the employee - although you like to think that does factor in, Zip can spit magma, after all – moreso the fact that Grillby very much prioritizes his pet over many things. You live in fear of the day someone accidentally brings Zip to harm.

Speaking of, you spot them trailing after two customers that have just entered, tail wagging much like a puppy’s as one of the humans tentatively pets their head. You whistle to get their attention, picking up a bag of treats from behind the counter and shaking it in front of you. The familiar noise has Zip scampering over to you in a matter of seconds. You hear one of the customers laugh at the sight, but you don’t have chance to stay and entertain. That energy now has to be put to use as you race Zip to the kitchen, keeping the bag out of their reach in the process. Coming to about your hip height-wise, this is no easy task.

“Yeah, yeah, I know- c’mon, then,” You slow as you pass through the doors, still holding the bag over your head and periodically pushing Zip’s face away whenever they try to jump up. At the back of the kitchen is the room generally reserved for the salamander’s things, although it’s not uncommon for some of the staff to hang out in there on their breaks. This is where you lead your excitable companion, dodging seemingly indifferent kitchen staff with mumbled apologies until you’re close enough to push open the door. “A’ight, buddy, here you go,” Once inside, you pull out some of the food from the bag and toss it, watching as Zip catches the doughnut midair. They really like the delicacies from an establishment a few blocks away – to be fair, they do look _really_ good – and it would seem today’s menu is powdered doughnuts.

As you continue throwing food for Zip to catch, you begin having to dodge both their tail and the stray globs of blue-tinted magma that escapes from their mouth. This is usually a rather troublesome activity, but with the energy boost you’re having a lot less trouble with it than usual. Which is good, because Zip seems extra excited today. They bounce around the room without a care in the world, snapping up food and apparently not noticing how much trouble they’re causing. Oh to be a giant salamander with no responsibilities except being fed and getting pet. 

Eventually, you run out of doughnuts for them to eat, and perch yourself up on one of the counters to wait for them to calm down a bit before attempting to leave. You learned that lesson the first time you were on Zip duty: never leave before they’re calm, lest you get tackled by a very excited reptile. It can take a while, but you don’t mind all that much – watching Zip do their thing is quite enchanting. The dark scales on their body shift and shimmer in the light, some of them parting in hairline cracks to reveal a reddish glow underneath. The magma that drips out of their mouth is mostly the same colour, although has a blue tint to it not unlike their owner’s own flames. Grillby’s fire in mainly green, though, with the blue coming secondary. You’ve yet to get tired of watching either of them, although it’s a little less rude to stare at Zip.

By the time they’ve calmed enough for you to leave, your energy seems to have depleted a bit. Hm. Well, it was nice while it lasted, if a bit excessive. You slip off the counter and pat the rough scales on Zip’s head as you make your way to the door, stepping over droplets of cooling magma as you do. Now your shift at work _really_ starts.

###### 

Your break couldn’t come soon enough. Everything always kicks off around mid-morning, seats are filled and noise levels rise as the breakfast rush commences, leaving you and the other employees with barely enough time to catch a breath. So when the time comes for you to sit down for a bit, you do so on the small ledge of a wall outside, having already left your apron in the staff room and reclaimed your phone from your bag. There are more messages from Papyrus, including the one you left earlier.

_**pyrus:** he mightve just put more magic in it than usual_  
_**pyrus:** he always did that when we were younger to help me out lol_  
_**pyrus:** idk if it works the same on humans tho_

Magic in the food? Sans _did_ mention that Monster food is infused with magic, but you didn’t realise he could manipulate how much was in it. Though, now that you think about it, that does make sense.

_**You:** Huh. Neat_  
_**You:** Is that why he was so insistent on cooking for me??_

_**pyrus:** nah thats just a sans thing_  
_**pyrus:** he gets frustrated when other people don do it ‘the right way’ so he jus does it himself_

Somehow, that doesn’t surprise you. Before you can voice (or text, rather) this opinion, Papyrus texts you again.

_**pyrus:** hey, look up_

You furrow your brows slightly, but do as he says. There’s nothing much for you to see at first, at least that you can tell. People are milling about here and there, some are just leaving through the doors next to you, the odd car occasionally passes by. You’re about to look down again to ask what he means, but you happen to catch sight of a particularly tall figure on the other side of the road, and your expression practically lights up. Honestly, how did you miss him? Papyrus is among the tallest monsters you’ve ever seen, you’d guess around ten or eleven feet altogether. Nevertheless, you wave at him and can just about see a grin when he realises you’ve spotted him. He glances down briefly - you hear your phone chime again – before heading towards you.

_**pyrus:** =< D_

You find yourself grinning as well; nothing like a gigantic skeletal sweetheart to brighten one’s mood, after all. 

Unfortunately, this doesn’t last; the slightly shorter Monster trailing behind Papyrus makes sure of that. You feel your grin become strained at the sight of Sans, arms crossed as he approaches you in all his annoying assholeish glory, and make a point to focus on his much more tolerable brother. What’s he doing here, anyway? You’ve never seen him around the diner before. As a matter of fact, you’ve never seen _either_ of them around here before. 

Papyrus offers a mock salute as he comes to a stop in front of you, one which you return with a much more genuine smile. His brother doesn’t bother to do even that, keeping his arms crossed and held closely to his chest. You stand – partially out of polite habit, partially to feel just a little bit taller next to them both – and copy his posture, albeit much more relaxed as you tilt your head back to acknowledge him. 

“Sans.” 

“Acquaintance.” 

You would’ve laughed if Papyrus hadn’t elbowed his brother in the side, in the next moment signing something with his hands so quickly you can hardly keep up. Sans turns to you, after watching the signing, and continues to make use of his deadpan tone to translate: “He says you’re dumb.” Papyrus evidently needs a better translator, as he is quick to shake his head and lightly swat the back of Sans’ skull. The latter chuckles – a quiet, brief rumbling sound that reminds you of how he growled yesterday – as Papyrus pulls out his phone again. You receive a text shortly after. 

_**pyrus:** i said ure BOTH dumb >=<[_  
_**pyrus:** but just for that hes dumber_

This time you do laugh, mostly because of how accurately Papyrus is mimicking the emoji face when you look up again. He’s holding his phone higher than usual, leaning to the side as Sans tries to see what he’s telling you. Considering that Sans only reaches to about his brother’s shoulder, he has to lean up on his toes to even attempt to snoop at the messages. 

Although the display is funny, you interrupt them after checking how much time you have left before you need to get back to work. “Not to pry, but what’re you guys doing here? Pretty sure I’ve never seen either of you at the diner.” 

“Papyrus insisted.” Somehow, you feel as though this is not the case, judging by the look Papyrus gives in response to the claim, but you roll with it for now. 

“Well, I’ve still got some time before I have to get back to work, so I guess I’ll just be out here if you need me,” You shrug, fully intent on relaxing outside for the remainder of your break. Sans seems happy to leave you to it, as well, quick to start towards the doors – he’s only stopped by Papyrus tugging his jacket’s sleeve and signing something once he has the other’s attention. 

You watch his hands move, if only out of curiosity, as you sit yourself back down on the ledge. It’s nothing like any sign language you’ve seen humans use, at least that you can tell. Many of the signs he’s using, none of which you recognise, are one-handed and sharp, creating precise gestures that you could only hope to guess the meaning of. Papyrus is very expressive, you notice, not only in his signing but in the changes of his face – they’re surprisingly fluid considering he’s made of bone. 

Such eloquence is directly contrasted by Sans, you notice, who responds to whatever his brother was saying with a flat “No.” Papyrus’ solution is to sign more insistently, while you’re left completely out of the loop as to what they’re talking about. Perhaps you’ll have to learn whatever kind of sign language your new friend is using… 

After a few more seconds of persistent signing and gruff responses, Sans sighs and begrudgingly turns to you once again. “He wants you to spend your break with us,” He finally translates, and continues with a light cough when Papyrus nudges him in the ribs, “Please.” 

You raise a curious eyebrow, glancing between the two before finally settling on Papyrus – he’s watching you with a hopeful glint in those lilac eyelights, and you’d hate to disappoint him. Besides, Sans seems to not like the idea and that’s all the incentive you need. So you grin, stand, and happily stroll towards the diner’s entrance. “Sure thing, I’m flattered you asked!” Like a true decently-mannered-and-very-petty person, you hold the door open for them and watch as Papyrus walks through with a skip in his step, pulling a scowling older brother behind him. 

Zip greets the three of you as soon as you step foot inside, absolutely delighted by the immediate attention they receive by Sans of all people. He crouches to scratch lightly under their chin, using the other hand to smooth over the scales of their head, only having to lean back slightly when magma starts to pool in their mouth. You can only watch for a moment before Papyrus has a gentle hold on your wrist and is guiding you to a booth. 

###### 

Apparently, that energy boost from this morning hasn’t completely left your system. Your leg is bouncing restlessly under the table, and you’ve given up on trying to stop it. If Sans _is_ at fault for this, you’re not sure whether to thank him or seriously consider punching him in his dumb face. Such is the duality of life, or whatever. 

Somewhere between when you left to order a drink and the time you sat back down at the booth, Sans had pulled out a packet of gummy bears and set them in the middle of the table, the packaging torn carefully down the middle for ease of access. You find this somewhat suspicious – you really hadn’t taken him for a sweets kind of guy – especially considering that neither of the brothers has touched them yet. Papyrus has been occupied with his milkshake for the past few minutes, doodling on a napkin with a pen he got from somewhere, while Sans is occupied with Zip continually headbutting his leg and demanding more chin scratches. 

You _are_ kind of hungry, though, having not eaten anything since breakfast, and something sweet sounds nice right about now. Perhaps not the healthiest option, but who’s going to stop you? Certainly not yourself, you think as you reach for a handful of the gummies nearest to you and shove them all in your mouth like some kind of cretin. 

Oh. Oh dear, this was a mistake. Your face instinctively scrunches up in response to the _ridiculously salty_ gummy bears you now have no choice but to bravely swallow, despite the overwhelming urge to spit them out onto the table. You force them down as quickly as you can, immediately springing for your drink to drown out the overwhelming taste. Dear gods that was _horrible,_ who the _fuck_ puts salt on candy-? 

A short bark of laughter from across the table draws your attention, and you look up to give your best death stare to your flatmate as he grins at your expense. He props his chin up on one hand, looking down at you as you steadfastly refuse the detach from your drink until all remains of salt are gone from your tastebuds. 

“Is a simple prank such as that all it takes to incapacitate you, human? I must say, I’m disappointed; although not surprised,” His tone is mocking, adopting a certain lilt that has you doubling down on your attempts at a death stare. Papyrus has looked up from his sketching now, and you can’t tell if that crooked grin is directed at you or his brother. 

You finally take a breath after downing the remains of your drink in one go, intent on telling Sans exactly where he can stick his dumb salty gummy bears, when a call of your name interrupts you. Grillby taps a finger to his wrist from his position at the counter, indicating that your break time is up, and you force a breath out through your nose before standing with a little more vigour than is perhaps necessary. Sans is still grinning at you, like the smug bastard he is, and you give a sharp ‘I’m watching you gesture’ before leaving without a word. 

This means _war._

**Notes for the Chapter:**

> this took a lot longer than i was intending, my apologies! but now the prank war can Officially Start >:3c
> 
> any comments/feedback is always appreciated, they make me super happy & encourage me to keep going! thank you to everyone who commented on the last chapter, too <3 <3

**Author's Note:**

> ∠( ᐛ 」∠)＿
> 
> i have!! zero self-control!!! and therefore decided that starting a new fic would be an Absolutely Wonderful Idea, What Are You Talking About-
> 
> a lot of sf!sans characterisations i see are,,,, not up to my personal tastes, so!! i took matters into my own hands - with any luck, you guys'll like my take on him and his bro too! :D please feel free to let me know what you think <3 unfortunately, updates are likely to be slow due to me being busy with college, just as a heads up! it'll be updated whenever i have spare time!


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